Temperature actuated connector

ABSTRACT

A temperature actuated device is disclosed which is capable of movement with a change in temperature of at least a portion of the device. The device has a first member which is fabricated from a material which undergoes a relatively large change in strength over the operating temperature range of the device. This first member may be operably connected to a second spring member so that movement of the second spring member causes movement of the first member. The second spring member preferably has a different strength-temperature characteristic so that the device will attempt to assume a first stable configuration at a first temperature and a different stable configuration at a second temperature.

United States Patent Otte [ TEMPERATURE ACTUATED CONNECTOR [75]Inventor: Richard F. Otte, Los Altos, Calif.

[73] Assignee: Raychem Corporation, Menlo Park,

Calif.

22 Filed: June 21,1972

[21] Appl. No.: 264,782

[52] US. Cl. 337/393 [51] Int. Cl. l-lOlh 37/46 [58] Field of Search337/393, 394, 395, 337/397, 123

[56] References Cited UNITED STATES PATENTS 3,613,732 lO/l97l Willson etal 337/393 FOREIGN PATENTS OR APPLICATIONS l8l,3l l 8/l954 Austria337/393 I [AW/Ill Jan. 1,1974

Primary Examiner-Harold Broome AttorneyCharles G. Lyon et a1.

[57] ABSTRACT A temperature actuated device is disclosed which iscapable of movement with a change in temperature of at least a portionof the device. The device has a first member which is fabricated from amaterial which undergoes a relatively large change in strength over theoperating temperature range of the device. This first member may beoperably connected to a second spring member so that movement of thesecond spring member causes movement of the first member. The secondspring member preferably has a different strength-temperaturecharacteristic so that the device will attempt to assume a first stableconfiguration at a first temperature and a different stableconfiguration at a second temperature.

12 Claims, 6 Drawing Figures TEMPERATURE ACTUATED CONNECTOR BACKGROUNDOF THE INVENTION The field of the invention is connectors of the typeuseful for forming a mechanical or electrical connection between two ormore members. The connector is temperature actuated so that at a firsttemperature, the

device will attempt to assume a first stable configuration and at asecond temperature it will attempt to reach a different stableconfiguration.

The device is particularly useful for forming an electrical andmechanical connection between a conductor and a printed circuit board.In the past, such connections have been commonly made by a plug-in typeconnection where the conductive board fits into a slot and a conductiveresilient member contacts a conductive portion of the board. Suchconnections have several disadvantages. First, the board is not tightlyheld in its plugged-in position. Secondly, the electrical connectiontends to degrade if the contact is not exercised. A soldered connectioncan be used to connect a conductor to a printed circuit board. Such aconnection does not have the plug in capability and requires resolderingat any time the printed circuit board needs to be removed or replaced.When multiple connections are involved, this disadvantage isparticularly acute An improved connector is disclosed in an applicationfiled by Otte and Fischer, US. Pat. Ser. No. 157,890

filed .lune 29, 1971 and assigned to the assignees of the presentinvention. This connector utilizes a heat recoverable metallic memberdisposed about a resilient member, such as the tines of a forked member.A conductor is inserted between the tines and the heat recoverablemetallic member is caused to shrink, thereby forcing the tines inwardlyand against the conductor. Such a device is somewhat limited in amountof movement, and is also relatively expensive. to fabricate and thus theneed for an improved connector exists.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a temperature actuated device which will form a first stableconfiguration at a first temperature, and a second stable configurationat a second temperature.

It is another object of the present invention to provide a reusableconnecting device capable of maintaining a secure contact at relativelyhigh temperatures.

The present invention is for a temperature actuated device comprising afirst member fabricated to be capable of undergoing a relatively largechange in force/deflection characteristics with temperature which memberis operably attached to a second spring member so that flexure of thesecond spring member causes a flexure of the first member. The firstmember and the second spring member are attached in an opposing mannerso that they tend to work against one another. When the temperature ofthe device is changed, the force/deflection characteristics of onemember changes with respect to the other member, and the device exhibitsmovement. When the first member is fabricated from a heat recoverablemetal such as an alloy of titanium and nickel, a connector capable ofoperation at high temperatures results since such alloys maintain theirstrength at high temperatures. Furthermore, when one of the members isconfigured so that it has a nonproportional load/deflectionrelationship, a connector which has the ability to snap from oneposition to a second position may result. A longitudinally loaded leafspring is particularly effective for this purpose.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a deviceof the present invention.

FIG. 2 is a side elevation of an alternate embodiment of a device of thepresent invention.

FIG. 3 is a side elevation of an alternate embodiment of a device of thepresent invention.

FIG. 4 is a side elevation of a spring member useful with the device ofthe present invention.

FIG. 5 is a side elevation of a spring member useful with the device ofthe present invention.

FIG. 6 is a side elevation of a spring member useful with the device ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The temperature actuated deviceof the present invention is caused to move by the action of two members,which are operably attached to one another in an opposing manner. Thematerials from which these members are fabricated have a differentstrength/temperature relationship so that the stable configuration ofthe device will vary with temperature.

Some materials such as heat shrinkable metals exhibit a relatively largechange in strength with temperature. An example of a suitable heatshrinkable metal is the alloys having about equal atomic proportions oftitanium and nickel. They typically have an austenitic secant modulus ofabout 12,000,000 PSI at a strain of k percent and a martensitic secantmodulus of about 850,000 PSI at a strain of 5 percent. This largedifference in secant modulus coupled with the large variation in strainmakes these alloys particularly suitable for use in thermally activateddevices of the sort described. Relatively large amounts of force andmovement per unit volume of material are attainable with them. Note alsothat the stress and strain applied must be such that the material doesnot deform permanently to any substantial degree during repeatedcycling. An initial permanent or plastic deformation is allowable but itmust not continue on cycling because if it does, the points betweenwhich the members move will vary with eacy cycle and that isundesirable.

Other alloys are known which exhibit a similar phenomena, and examplesof such alloys are disclosed in A. Nagasawa, 31 J. Phys. Soc. Japan No.1, July, 1971 pp. 136-147. Examples include cadmium-gold,copperaluminum-nickel, indium-thallium, uraniummolybdinum anduranium-niobium. Some polymers and elastomers are also known to exhibitarelatively large modulus change with temperature and may also be used inthe practice of the present invention.

The members of the device of the present invention can be of practicallyany configuration. For instance, the device of FIG. 1 utilizes a curvedend cantilever spring 20 which is operably attached to a longitudinallyloaded leaf member 21. Spring 20 is inserted through an opening in base22. If member 21 is fabricated from a material which has a relativelylow modulus at low temperatures, and spring 20 is fabricated from amaterial which has a relatively high modulus at low tempera-- ture isincreased, the longitudinal force exerted by member 21 also increases,and it will extend in the position shown by the solid lines in FIG. 2.If a circuit board 23 is placed between the device and base 22, a strongcontact will be made between the printed circuit board and contact point24 of spring when member 21 is at a temperature at which it has arelatively high strength. Member 21 is held in spring 20 by stop 25 andindentation 26. Stop 25 also positions spring 20 in base 22.

The device shown in FIG- 1 represents a particularly effectivetemperature activated device for a reason which is not readily apparent.This reason relates to the load/deflection characteristics of member 21.Although member 21 is generally in the shape of a leaf spring, it is notloaded near its midpoint, but instead is only longitudinally loaded. Byso loading member 21,- it will exert a relatively large force in alongitudinal direction when it is nearly straight. That is, it takes arelatively large force to deform member 21 from its relaxed position,but once it has been partially deformed it will actually take less forceto cause further deformation. Thus, unlike most springs, the load todeflection ratio is not constant but instead varies depending upon theamount of deflection. Stated differently, if a plot is made of loadversus deflection for most'springs, a straight line will result whereaswith a longitudinally loaded leaf spring a curved line will result.

By choosing the proper combination of load/deflection characteristics ofsprings 20 and member 21, it is possible to'create a device which willtend to snap open and closed with a relatively small temperature change.

Although a longitudinally loaded leaf spring comprises a particularlysimple method for achieving this snap action, other nonlinear springsmay also be used. For instance, a Belleville spring may be configured tohave a highly nonlinear load/deflection curve. Furthermore, if the ratioof the height to the thickness of the Belleville spring is properlychosen, the load/deflection curve may have a peak which may be utilizedto produce a snap effect. See, for instance, Machine Design by J. E.Shigley -McGraw-Hill, 1956 at FIG. 7-15 on page 237 which showsload/deflection curves for a series of different Belleville springswhich curves are incorporated by reference herein.

One method of achieving this snap action is by choosing a member whichhas a force/deflection curve which has a peak therein. That is, theforce deflection curve should reach a maximum followed by at least someportion of decreasing slope. For instance, the force/deflection curve ofthe first member might look like:

DEFLECTION A device with a snap action would result if the second memberwas connected to the first member in such a way that the deflection ofthe first member was on the left-hand side of the peak when the devicewas in a first 4- stable position and on the right hand side of the peakwhen the device was in its second stable position.

Several shapes of devices exhibit a force deflection/- curve with somenegative slope and two examples include some Belleville springs (e.g.Belleville springs having an ODof 5 inches, an ID of 2 A inches, athickness of 0.040 inches and a height to thickness ratio greater thanabout 2.0) and longitudinally loaded leaf springs.

A slightly different configuration of temperature actuated device isshown in FIG. 2. A fork spring has a tine 31 having a contact point 32.A longitudinally loadedmember 33 is held in grooves 34 and 35 of spring30. Spring 30 is held in an opening 36 in base 37.

In order to bring about movement of the device, the temperature of thedevice of FIG. 2 is first set so that member 33 requires a relativelylow force. to cause a deflection. For instance, if spring 33 isfabricated from an alloy having major proportions. of titanium andnickel, the temperature should be decreased in order to convert thetitanium-nickel alloy to its martensitic phase configuration. As statedabove, this decreases the force it exerts and thus weakens it withrespect to spring 30 which then can deform member 33 to a position shownby the phantom lines in FIG. 2. This cooling may be carried out by meanssuch as by spraying with a low boiling liquid which has beenpressurized. Suitable liquid coolants include tetrafluoromethane,chlorotrifluoromethane and trifluoromethane. Alternatively, cooling maybe carried out by contact with ice, by liquid nitrogen, or the like.Printed circuit board 38 is then inserted against a portion of base 37and the temperature of the device is then changed in order to increasethe force exerted by member 33 which then forces spring 30 and contactpoint 32 to the position shown by the solid lines in FIG. 3. In thisposition, it is capable of exerting a relatively large force againstboard 38, since spring'33 is in a nearly columnar position.

The device of FIG. 3 closes against an object when the leafspring-shaped member is in its low strength configuration. Cantileversprings 40 and 41 are mounted through base 42, and a member 43 is heldin notches 44 and 45 of springs 40 and 41. Springs 40 and 41 arefabricated from a material which exhibits a relatively large change inforce/deflection characteristics with temperature whereas member 43 isfabricated from a conventional material such as spring steel. When thetemperature of the device of FIG. 4 is such that springs 40 and 41 arein their low strength configuration, the member 43 will force springs 40and 41 apart into a position indicated by the phantom lines of FIG. 3.When the temperature is changed so that the force/deflectioncharacteristics of springs 40 and 41 is relatively high with respect tothe modulus of member 43, the device will close to the position shown bythe solid lines of FIG. 3. Thus, if an object 46 is placed between thecontact points 47 and 48 of springs 40 and 41, it will be held as shownin FIG. 4.

Various spring configurations are shown in FIGS. 4 through 6. Thesesprings can be used in devices of the type shown in FIGS. 1 through 3.Although it is advantageous that the member which is analogous to member21 of FIG. 1 have a nonlinear load/deflection curve, this is notessential, since the device will nonetheless be operative if the memberhas a constant load/deflection ratio. Although the devices described inFIGS. 1 and 2 were described as if the longitudinal leaf spring-likemember was fabricated from a material whose modulus changedsubstantially with temperature, the device could also be made where themember which corresponds to member 21 of FIG. 1 is fabricated from amaterial having a relatively constant load/deflection characteristicswith temperature. The other spring should then be fabricated from amaterial whose modulus changed substantially with temperature. Forinstance, if the device of FIG. 1 were fabricated so that spring 20 wasmade from a titanium/nickel alloy, the device would tend to seek theposition shown by the solid lines in FIG. 1 when spring 20 is in a lowmodulus configuration. Similarly, the device of FIG. 1 would tend toseek the shape shown by the phantom lines shown in FIG. 1 when spring 20was in a relatively high modulus configuration.

It is significant to note that the movement brought about in the devicesof'the present invention do not require that there be a dimensional orlength change in one of the spring members. It is a change inload/deflection characteristics which brings about a movement ratherthan a dimensional change. In this way, the devices of the presentinvention differ in kind from bimetallic members which depend upondifferential expansion or contraction with temperature. Changes inproperties such as the secant modulus bring about a change in theload/deflection characteristics of a spring. For example, the alloyshaving about equal atomic proportions of titanium and nickel typicallyhave a secant modulus of about 850,000 PSI at a strain of 5 percent whenin the martensitic phase and a secant modulus of about 12,000,000 PSI ata strain of A percent when in the austenitic phase.

The devices of the present invention have the potential advantage ofbeing fabricated wholly from metals, and thus can be made to withstandgreat temperature extremes. The alloy TiNi remains strong at hightemperatures; for instance, the Youngs modulus of TiNi at 600C is about14,000,000 and the strength of many spring steels remains high at 600 C.

The present embodiments of this invention are thus to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims rather than by theforegoing description. All changes which come within the meaning andrange of equivalency of the claims therefore are intended to be embracedtherein.

I claim:

l. A snap-action temperature actuated spring device comprising acombination of first and second spring members bearing against oneanother such that flexure of one such member toward its relaxed positioncauses flexure of the other such member away from its respective relaxedposition, one of said members undergoing a substantial change in modulusin passing from a first to a second temperature within the temperatureoperating range of said device while the modulus of the other suchmember remains relatively constant such that, absent external restraint,said combination assumes a first stable configuration at one temperaturewithin said range and another stable configuration at another; saidfirst member having a non-linear loaddeflection curve having a peaklying within the useful deflection range of said device such that inpassing from one to another of those temperatures at which said stableconfigurations respectively obtain the flexure of said members causesdeflection of said first member from one to the other side of said peakin the absence of external restraint.

2. The device of claim 11 wherein said first member undergoes asubstantial change in modulus in passing from a first to a secondtemperature within the temperature operating range of said device.

3. The device of claim 2 wherein said first member is a longitudinallyloaded leaf spring which is operably connected to said second springmember.

4. The device of claim 2 wherein said second spring member is a curvedend cantilever spring and wherein said first member is positioned acrossthe curved end thereof.

5. The device of claim 2 wherein said second spring member is a forkspring having at least two tines and wherein said first member ispositioned therebetween.

6. The device of claim 5 wherein said first member is fabricated from ametallic alloy composed of major porportions of titanium and nickel.

7. The device of claim I wherein said second member undergoes asubstantial change in modulus in passing from a first'to a secondtemperature within the temperature operating range of said device.

8. An assembly comprising a first electrode and a spring deviceaccording to claim 2, said second member serving as a second electrodeand being urged (1) into electrical contact with said first electrode bysaid first member at a temperature at which said first stableconfiguration would obtain absent the restraint of said .firstelectrode, and (2) out of contact with said first electrode at a lowertemperature at which said second stable configuration obtains.

9. An assembly comprising a temperature actuated spring devicecomprising a combination of first and second spring members bearingagainst one another such that flexure of one such member toward itsrelaxed position causes flexure of the other such member away from itsrespective relaxed position, said first member undergoing a substantialchange in modulus in passing from a first to a second temperature withinthe temperature operating range of said device while the modulus of saidsecond member remains relatively constant such that, absent externalrestraint, said combination assumes a first stable configuration at onetemperature within said range and another stable configuration atanother; said assembly further comprising a first electrode and saidsecond member serving as a second electrode which is urged (11) intoelectrical contact with said first electrode by said first member at atemperature at which said first stable configuration would obtain absentthe restraint of said first electrode, and (2) out of contact with saidfirst electrode at a lower temperature at which said second stableconfiguration obtains.

10. An assembly according to claim 9 wherein said first member is alongitudinally loaded leaf spring which is operably connected to saidsecond spring member such that said first member assumes a near columnarshape when said second member electrically contacts said firstelectrode.

1 l. The device of claim 10 wherein said second member is a curved endcantilever spring and wherein said first member is positioned across thecurved end thereof.

12. The assembly of claim 10 wherein said second member is a fork springhaving at least two tines and wherein said first member is positionedtherebetween. i

1. A snap-action temperature actuated spring device comprising acombination of first and second spring members bearing against oneanother such that flexure of one such member toward its relaxed positioncauses flexure of the other such member away from its respective relaxedposition, one of said members undergoing a substantial change in modulusin passing from a first to a second temperature within the temperatureoperating range of said device while the modulus of the other suchmember remains relatively constant such that, absent external restraint,said combination assumes a first stable configuration at one temperaturewithin said range and another stable configuration at another; saidfirst member having a non-linear load-deflection curve having a peaklying within the useful deflection range of said device such that inpassing from one to another of those temperatures at which said stableconfigurations respectively obtain the flexure of said members causesdeflection of said first member from one to the other side of said peakin the absence of external restraint.
 2. The device of claim 1 whereinsaid first member undergoes a substantial change in modulus in passingfrom a first to a second temperature within the temperature operatingrange of said device.
 3. The device of claim 2 wherein said first memberis a longitudinally loaded leaf spring which is operably connected tosaid second spring member.
 4. The device of claim 2 wherein said secondspring member is a curved end cantilever spring and wherein said firstmember is positioned across the curved end thereof.
 5. The device ofclaim 2 wherein said second spring member is a fork spring having atleast two tines and wherein said first member is positionedtherebetween.
 6. The device of claim 5 wherein said first member isfabricated from a metallic alloy composed of major porportions oftitanium and nickel.
 7. The device of claim 1 wherein said second memberundergoes a substantial change in modulus in passing from a first to asecond temperature within the temperature operating range of saiddevice.
 8. An assembly comprising a first electrode and a spring deviceaccording to claim 2, said second member serving as a second electrodeand being urged (1) into electrical contact with said first electrode bysaid first member at a temperature at which said first stableconfiguration would obtain absent the restraint of said first electrode,and (2) out of contact with said first electrode at a lower temperatureat which said second stable configuration obtains.
 9. An assemblycomprising a temperature actuated spring device comprising a combinationof first and second spring members bearing against one another such thatflexure of one such member toward its relaxed position causes flexure ofthe other such member away from its respective relaxed position, saidfirst member undergoing a substantial change in modulus in passing froma first to a second temperature within the temperature operating rangeof said device while the moduLus of said second member remainsrelatively constant such that, absent external restraint, saidcombination assumes a first stable configuration at one temperaturewithin said range and another stable configuration at another; saidassembly further comprising a first electrode and said second memberserving as a second electrode which is urged (1) into electrical contactwith said first electrode by said first member at a temperature at whichsaid first stable configuration would obtain absent the restraint ofsaid first electrode, and (2) out of contact with said first electrodeat a lower temperature at which said second stable configurationobtains.
 10. An assembly according to claim 9 wherein said first memberis a longitudinally loaded leaf spring which is operably connected tosaid second spring member such that said first member assumes a nearcolumnar shape when said second member electrically contacts said firstelectrode.
 11. The device of claim 10 wherein said second member is acurved end cantilever spring and wherein said first member is positionedacross the curved end thereof.
 12. The assembly of claim 10 wherein saidsecond member is a fork spring having at least two tines and whereinsaid first member is positioned therebetween.